The entire solution from above is distilled until the temperature reaches 93 deg

Question

The entire solution from above is distilled until the temperature reaches 93 degree C. The volume of distillate is 65.0 mL and the density of the distillate is determined as follows. An empty 50 mL beaker has a mass of 26.4785 g. 10.0 mL of distillate is pipetted into the 50 mL beaker. The beaker plus distillate has a mass of 34.8785 g. Answer the following: i. What is the density of the distillate? ii. What is the concentration of ethanol in the distillate? iii. Did the distillation work as expected? Explain your answer using the experimental results.

Explanation / Answer

(i)

Density of distillate = Mass of distillate/Volume

Given: volume pipetted in 50 mL flask = 10 mL

Mass of this 10 mL distillate = 34.8785-26.4785 = 8.4 g

So, density = 8.4/10 = 0.84 g/mL

(ii)

Density of pure ethanol = 0.789 g/mL

Assume we take 100 mL of this distillate.

Mass of this much distillate = 100*0.84 = 84 grams

Assume 'x' grams ethanol is present.

So, volume of ethanol = x/0.789 mL

Mass of water = 84-x

So, volume of water = (84-x)/1 = 84-x

Total volume = x/0.789 + 84 - x = 100

Solving we get:

x = 59.83 g

So, moles of ethanol present in 100 mL (0.1 L) solution = 59.83/46.06 = 1.298

So, molarity = moles/volume in liters = 1.298/0.1 = 12.98 M

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